Variable range hopping in graphene antidot lattices



We investigate the low temperature electrical transport mechanism in graphene antidot lattices. While the antidot diameter is kept constant at 50 nm, the center-to-center spacing between the antidots is varied from 80 to 200 nm in cubic arrangement. Our temperature dependent charge transport data reveal that electrical conduction in the samples is governed by variable range hopping (VRH) between localized states within a band gap. Upon decreasing the nanohole spacing the localization becomes stronger and the transport mechanism changes from 2D Mott VRH to Efros–Shklovskii (ES VRH). Concomitantly, a soft gap emerges due to the stronger localization and the increased Coulomb interactions between the localized states, which are most likely located at the nanohole edges. The Coulomb gap (CG) decreases linearly with increasing charge carrier density. Stronger localization with an increased CG is observed for thermally annealed samples with reduced doping.